It is known that magnetic-type rotation position detection devices are able to detect a rotation position of a detection target that moves relative to a reference member. This type of rotation position detection device includes two magnets (or “magnetic flux generators”) and two yokes (or “magnetic flux carriers”) that form a closed magnetic circuit, and a magnetic flux density detection unit (e.g., a Hall element) disposed within the closed magnetic circuit. For example, the magnets and yokes may be disposed on the detection target, and the magnetic flux density detection unit may be disposed on the reference member. Magnetic flux density passing through the magnetic flux density detection unit changes according to the position of the magnetic flux density detection unit with respect to the yokes. As such, the rotation position detection device detects the rotational position of the detection target based on the magnetic flux density passing through the magnetic flux density detection unit.
For example, JP 2014-126548 A discloses a position detection device that includes an inner yoke and an outer yoke, the inner yoke being disposed radially inward of the outer yoke. The inner yoke is shaped such that toward either end in a rotational direction, the inner yoke is increasingly displaced radially inward and spaced away from a trajectory of a Hall element. Further, the outer yoke is shaped such that toward either end in the rotational direction, the outer yoke is increasingly displaced radially outward and spaced away from the trajectory of the Hall element. Accordingly, a gap between the two yokes is greater at the ends of the yokes than at the centers of the yokes, and increases in magnetic flux density flowing to the Hall element may be curtailed at the end portions of the gap. As a result, linearity of the output signal from the Hall sensor may be improved, i.e., a relationship between the rotational position of the detection target and the magnetic flux density passing through the Hall element may approach a linear relationship.